For conservation to be successful it is necessary to take into consideration that it is a characteristic of man that he can only be relied upon to do anything consistently which is in his own interest. He may have occasional fits of conscience and moral rectitude but otherwise his actions are governed by self-interest. It follows then that whatever the moral reasons for conservation it will only be achieved by the inducement of profit or pleasure.

World Wildlife Fund: British National Appeal Banquet, London (1962) - The Environmental Revolution: Speeches on Conservation, 1962–77 (1978)